No abstract

The problem of road safety does not lose its relevance in our time. The condition and performance of tires has a significant impact on the safety of road transport. Unfortunately, the tire pressure monitoring requirements of the developers are not always met. Naturally, now some modern cars are equipped with various systems for monitoring and even adjusting the internal tire pressure. However, there are relatively short periods of time during which the pressure and temperature in the tire change dramatically, and hence its other performance and properties. First of all, we are talking about dramatically changing weather conditions and the starting movement of the car. And then additional monitoring of tire pressure is needed. Goal. On the basis of the experimental studies carried out, to obtain the dependence of the temperature and pressure changes inside the tire on the time of car movement. To determine the initial period of time of car movement until the pressure and temperature in the tested tires stabilize. Methodology. The work used the technique of both bench tests of tires in the laboratory and road tests under real weather conditions by car. Based on the numerical processing of the experimental results, dependencies were obtained, using which it is possible to determine the increase in temperature and pressure in tires in the mode of starting movement of the car. Results. The analysis of scientific publications on this topic is performed. The time from the beginning of the car to the stabilization of temperature and internal pressure in the tires is determined, as well as the increase in temperature and pressure inside the tire during this period. The method of determining the starting time of the car to stabilize the internal pressure and temperature is proposed.  Originality. In this work, for the first time, a method is proposed for assessing the temperature and internal pressure in tires in the mode of starting movement of the car, which makes it possible to obtain dependencies without resorting to further experimental studies. Practical value. Using the obtained dependencies for certain tires and under different weather conditions, it is possible to predict the change in tire pressure at the starting mode of the car's movement, and therefore make adjustments to this value, if necessary, which will have a positive effect on the safety of moving vehicles.

Problem. From the condition of the tires and their correct choice depending on the weather conditions, first of all, the indicators of many operational properties of the car depend. The internal pressure and temperature of the tire increases during driving, as a result, there is a significant effect on the rolling resistance of the tire. At high values of the rolling resistance coefficient, first of all, fuel consumption increases, tire wear increases, etc. It is important to know how the rolling resistance coefficient changes during the starting period of motion. Goal. The purpose of this work is to determine the starting mode of motion time for specific vehicles. Based on the obtained dependences of the internal pressure and temperature of the tire on time, it is necessary to evaluate how the rolling resistance coefficient changes. Methodology. As a result of experimental studies, on vehicles equipped with tires of various sizes and seasonality, the dependences of the pressure and temperature of the tire material at three points (tread zone, shoulder part and sidewall) were obtained. Using the results of the experiment, as well as based on the dependencies presented in scientific papers devoted to the study of the performance characteristics of car tires, an indirect assessment of the rolling resistance coefficient when driving in the starting mode is made. Results. The value of the increase in the internal pressure of the gas filler in the tire has been established and the driving time for the studied vehicles in the starting mode has been determined. The most intense temperature rise is observed in the shoulder area of the tires. The temperature of the surface layer of winter tires increases less than summer tires, and, accordingly, driving on winter tires is safer at temperatures close to 0°C and below. Originality. A technique for indirectly assessing the rolling resistance of a car tire when driving in the starting mode (on "cold" tires) is presented, that is, knowing how the internal air pressure and tire temperature change, it is possible to predict a change in the rolling resistance coefficient. Practical value. Using the dependences obtained as a result of an indirect assessment of the rolling resistance of car tires, one can judge the value of the rolling resistance coefficient without resorting to experiments. The well-known assertion that it is necessary to timely replace summer tires with winter ones (when the ambient temperature can reach +5 ° C and lower) is confirmed, thereby significantly improving road safety.

The review of the literature devoted to the research of public transport vehicle (PTV) dwell time required for passenger boarding-deboarding at a stop confirms the importance of taking this time into account when modelling passenger transportation. The data about the dwell time were collected in different time periods for different PTVs in various cities and countries. Thus, there is no general model allowing to define the distribution parameters of dwell time variable and answer the question on the regularities in time values. So, the research of the PTV dwell time at the public transport stops in Kharkiv remains actual. Goal. The search of the regularities in transport system performance indicators including PTV dwell time at a stop will allow to apply relevant mathematical methods for the development of the forecast models which are valuable in the field of organization of passenger transportation and servicing. Methodology. The developed methodology to collect data about PTV dwell time at the stops will allow receiving high-quality survey data. The designed survey sheets enable a surveyor to record all needed information and prepare it for processing. The collected data will allow to define the distribution of the PTV dwell time at a stop. Results. The conducted PTV dwell time survey allowed to collect the sufficient amount of data to estimate the distribution of this variable. During the research, it was determined that the empirical dwell time distribution can be well described with the theoretical gamma distribution. The latter distribution appeared to be applicable for all surveyed PTVs. Originality. The defined distribution of the PTV dwell time at a stop for passenger boarding-deboarding allows receiving the results of passenger flows modelling which are more precise compared to the modelling with no dwell time consideration. The use of the dwell time regularities in the procedure of passenger flows assignment results in the increased precision of flow volumes estimation by up to 14.9 % – from 2.28 % to 1.94 %. Practical value. The received results support the fact that the research of PTV dwell time at a stop is actual, and the solution of the task of dwell time distribution estimation will make it possible to improve passenger flows modelling in public transport route systems.

АВТОТРАНСПОРТНЫЕ СРЕДСТВА УДК 629.3.027.5=111 ШУМ КАК КОСВЕННЫЙ КРИТЕРИЙ ОЦЕНКИ КРИТИЧЕСКОЙ СКОРОСТИ АВТОМОБИЛЬНОЙ ШИНЫ ПРИ ГИДРОПЛАНИРОВАНИИ В.А. Карпенко, проф., д.т.н., К.В. Масляев, студ., Харьковский национальный автомобильно-дорожный университет Аннотация. Рассмотрен альтернативный метод определения критической скорости качения автомобильных шин с различными рисунками протектора при гидропланировании. Данный метод основан на регистрации шумоизлучения шины при движении по мокрому дорожному покрытию. Ключевые слова: автомобильная шина, шум, критическая скорость, гидропланирование автомобиля, коэффициент насыщенности рисунка протектора. ШУМ ЯК НЕПРЯМИЙ КРИТЕРІЙ ОЦІНКИ КРИТИЧНОЇ ШВИДКОСТІ АВТОМОБІЛЬНОЇ ШИНИ ПРИ ГІДРОПЛАНУВАННІ В.О. Карпенко, проф., д.т.н., К.В. Масляєв, студ., Харківський національний автомобільно-дорожній університет Анотація. Розглянуто альтернативний метод визначення критичної швидкості кочення автомобільних шин з різними рисунками протектора при гідроплануванні. Вказаний метод базується на реєстрації шумовипромінювання шини під час руху по мокрому дорожньому покриттю.